Wireless communication systems, such as the 3rd Generation (3G) of mobile telephone standards and technology, are well known. An example of such 3G standards and technology is the Universal Mobile Telecommunications System (UMTS™), developed by the 3rd Generation Partnership Project (3GPP™).
The 3rd and 4th generations of wireless communications, and in particular systems such as LTE, have generally been developed to support macro-cell mobile phone communications. Here the ‘phone’ may be a smart phone, or another mobile or portable communication unit that is linked wirelessly to a network through which calls are connected. Henceforth all these devices will be referred to as mobile communication units. ‘Calls’ may be data, video, or voice calls, or a combination of these. An increasing proportion of communications involve data rather than voice. Communications are technically referred to as being a ‘connection’, rather than a ‘call’.
Macro cells utilize high power base stations to communicate with wireless communication units within a relatively large geographical coverage area. The coverage area may be several square kilometers, or larger if it is not in a built-up area.
Typically, mobile communication units communicate with each other and other telephone systems through a network. In a 3G system, this is the ‘Core Network’ of the 3G wireless communication system, and the communication is via a Radio Network Subsystem. A wireless communication system typically comprises a plurality of Radio Network Subsystems. Each Radio Network Subsystem comprises one or more cells, to which mobile communication units may attach, and thereby connect to the network. A base station may serve a cell with multiple antennas, each of which serves one sector of the cell. Often a cellular wireless communication system is described as comprising two parts: the network; and the mobile communication units.
FIG. 1 provides a perspective view of one prior art wireless communication system 100. The system of FIG. 1 comprises a network of base stations, comprising BS1 with reference 110, BS2 with reference 120, BS3 with reference 130, BS4 with reference 140 and BS5 with reference 150. Only one mobile communication unit 105 is shown. In a real network, there may be anywhere from thousands to millions of mobile communication units.
A base station such as 110 communicates with mobile communication unit 105. Base station 110 allows mobile communication unit 105 to place calls through the network, and receive calls routed through the network to base station 110.
Base station 140 has been shown as having a coverage area 142. If base station 140 had an omnidirectional antenna, and the terrain were flat, then coverage area 142 might be circular. However, both the shape and extent of the coverage areas of a typical base station depend on many variables, and may change with time.
Controller 160 manages calls within the wireless communication system 100. Controller 160 would be linked to all the base stations BS1-BS5, but the links are not shown in order to keep FIG. 1 simple to interpret. Controller 160 may process and store call information from the base stations, plus many other base stations not shown in FIG. 1. In a UMTS network, controller 160 may be linked to the base stations via one or more Radio Network Subsystems.
There may be significant advantage in knowing: (i) information about coverage and quality of service in each part of the network; and (ii) where a mobile communication unit 105 is located in wireless communication system 100. Prior art wireless communication systems have provided a variety of solutions to the problem of ‘geolocating’ mobile communication unit 105. One known solution involves providing specific equipment within the mobile communication unit that can measure location, such as a GPS unit. However, many users switch off the GPS function on their mobile communication units. Partly as a consequence, reported GPS details are highly infrequent. As little as one call in ten-thousand connections might report a GPS coordinate.
One prior art solution indicates that absolute power transmission levels can be used to geo-locate the mobile station. See for example “Mobile Cellular Location Positioning: An Approach Combining Radio Signal Strength Propagation and Trilateration”, M. F. Khan, Masters Thesis, University of Johannesburg, November 2009 which is herein incorporated by reference in its entirety. Co-pending U.S. patent application Ser. No. 13/311,132, with applicant reference OPT004P326, which is also incorporated by reference in its entirety, indicates that differential power levels can be used to geo-locate a mobile communication unit. Patent application WO2010/083943A shows a further technique, which uses signal strength and timing data derived from the mobile communication unit itself, along with network configuration data provided by the network operator, to locate the mobile communication unit.
Co-pending U.S. patent application Ser. No. 13/369,591, with applicant reference OPT004P330, and is hereby incorporated by reference in its entirety, indicates that a database of ‘known’ signatures can be used to aid in locating a mobile communication unit operating in a mobile communications system. Each known signature comprises a location measurement or estimate, together with radio frequency and other measurements that were obtained by a mobile communication unit at that location at a particular time. Examples of the ‘other measurements’ that may be obtained by a mobile communication unit are: control information; a set of cells observable by the first mobile communication unit; and received power level information, for signals received from the observable cells. The use of this database of known signatures enables position estimates to be derived, at least for any mobile communication devices that report similar values of the radio frequency and other measurements to those of a known signature.
The invention of U.S. patent application Ser. No. 13/369,591 only allows the estimation of the position of a mobile communication device if there is a match between a known signature in the database and the values of the radio frequency and other measurements reported by that mobile communication device. This approach therefore relies on the database having very many known signatures. For a cellular two-way radio system, the database may require hundreds of thousands or millions of known signatures. Obtaining these known signatures may be difficult. One approach is to collect signatures with location information by drive-testing and/or indoor-walk-testing. Such testing relies on moving a test mobile communications device through a network, in order to collect accurate position measurements from the mobile communication device and at the same time measure, for those positions, the values of various radio frequency and other measurements.
Drive-testing and indoor-walk-testing have the disadvantages that:
(i) Drive-test and walk-test signatures may not be easily obtained in the areas most frequented by actual users. This is because some areas are not accessible for either drive- or walk-testing, such as private company premises.
(ii) Signatures can be expensive to obtain over extensive areas, since they require intensive use of personnel and, where relevant, vehicles.
Signatures obtained from drive- or walk-testing can be augmented by selecting data from the Operation Support System (OSS) of the mobile communications system. The OSS holds measurements made by many or all of the subscriber mobile communication units that operate in a mobile communications system. Some or all of the calls made during drive- or walk-testing will result in a record being created in the OSS. In some systems, the record of the call from the test mobile communications device and the corresponding record from the OSS both contain identification information for the test mobile communications device. If this is the case, then the common identification information can be used to retrieve the correct individual record from the OSS, by matching its identification information with the identification information for the test mobile communications device used in the drive or walk testing. Then the records can be combined. In particular, the record retrieved from the OSS may contain measurements made by the mobile communications system that can be added to the record of the same call that was made by the test mobile communications device itself as part of drive or walk testing.
Phone applications, usually referred to as ‘apps’, are becoming common on mobile communication units. Various phone apps facilitate an enormous range of tasks, and usually involve users of mobile communication units providing some data during the course of using the phone apps. However, that information tends not to be captured or be available for use by the wireless communications system, but rather for use by social media websites and other commercial service providers.
Known cellular wireless communication systems tend to lack data about the performance of the network at specific locations. These may be geographical areas in which network equipment has been newly installed, for example. Another example might be a network that relied on drive- or walk-testing for data about the performance of the network, and such data was unobtainable where vehicles and walk testers are not permitted access. Hence, there is a need for an improved provision of coverage and capacity data for a mobile communications system such as an LTE, GSM or UMTS network
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve under-standing of embodiments of the present invention.